P0585 — Cruise Control Multi-Function Input “A”/”B” Correlation #

Please note: The label and wording for DTC P0585 can vary depending on the vehicle manufacturer (OEM). It’s important to consult official repair information for your specific model.

• P0585 – Cruise Control Multi-Function Input “A”/“B” Correlation (Generic/Multiple OEMs)
• P0585 – Cruise Control Switch “A”/“B” Correlation (Ford, Hyundai)
• P0585 – Cruise Control System Input Mismatch (Toyota, Lexus)
• P0585 – Cruise Control Switch Input Malfunction (Honda, Acura)

Code summary for P0585 #

P0585 is an OBD-II diagnostic trouble code (DTC) that indicates a mismatch or unexpected correlation between signals from the cruise control’s multi-function switch, commonly known as the “A” and “B” input circuits. In plain language, your vehicle’s computer (the ECU—Engine Control Unit) has detected that the signals sent by the cruise control switch don’t agree with each other or with expected values. This code is designed to prevent unsafe cruise control operations, as mismatched inputs could cause the system to misbehave. The issue can stem from electrical faults, a faulty switch, or even damaged wiring. While this code won’t typically leave you stranded, it does mean your cruise control system may be disabled until you address the root cause.

Frequent symptoms for code P0585 #

When P0585 is stored, you’ll likely notice issues related to cruise control operation. The most common symptom is the cruise control system not working at all. In some cases, you might see a warning light or a message on the dashboard, signaling a problem with the system. Rarely, erratic or unreliable cruise control behavior can occur, but most modern vehicles will simply disable cruise control for safety reasons.

• Cruise control fails to engage or operate
• Cruise control disengages unexpectedly
• Warning indicator illuminated (e.g., “CRUISE” light flashing or on steady)
• Message on dash such as “Cruise Control System Fault”
• No effect on engine drivability or performance (outside cruise control)

Likely causes for P0585 (by frequency) #

The root causes for a P0585 code generally relate to the cruise control switch assembly, its electrical circuits, or the connections between them. The most common cause is a faulty or worn cruise control switch, but issues can also arise from wiring faults or corrosion at connectors. Less frequently, the problem may be traced to the vehicle’s ECU or a software issue, especially if the vehicle has been subject to aftermarket modifications.

1. Faulty cruise control multi-function switch (most common)
2. Open or short in the cruise control switch wiring harness
3. Corroded, loose, or damaged electrical connectors
4. Faulty clockspring (steering wheel wiring rotary connection)
5. ECU malfunction (rare, but possible)
6. Aftermarket accessories interfering with cruise control circuits

Step-by-step diagnostic for P0585 #

A logical diagnostic process helps avoid unnecessary part replacement. Start by confirming the code and checking the system’s basic operation, then move on to inspecting components and wiring. Here’s a proven sequence:

• Verify the presence of code P0585 with a scan tool and note any related codes.
• Check if cruise control engages or any warning lights/messages are present.
• Inspect the cruise control switch for obvious physical damage or stickiness.
• Test the switch’s “A” and “B” output signals using a wiring diagram and multimeter; compare readings to OEM specs.
• Visually inspect wiring and connectors between the switch and ECU for broken, frayed, or corroded wires.
• Check the clockspring (if applicable) for continuity—especially if other steering wheel controls are also malfunctioning.
• If all checks pass, consider testing the ECU input pins and performing a relearn or reset if recommended by the manufacturer.
• Clear the code, road test, and see if P0585 returns.

Possible repairs for P0585 #

Repair actions depend on the diagnostic findings. The most frequent fix is replacing the cruise control switch, but sometimes repairs are as simple as cleaning a connector. Here are the usual solutions:

• Replace faulty cruise control switch
• Repair or replace damaged wiring in the cruise control circuit
• Clean or tighten corroded or loose connectors
• Replace clockspring if continuity tests fail
• Reflash or update ECU software (only if recommended and other causes have been ruled out)
• Remove or correct any interfering aftermarket electronics

Is it safe to drive with code P0585? #

Yes, you can generally drive your vehicle with code P0585 present, as it does not affect primary driving functions or engine performance. However, the cruise control system will usually be disabled for safety, so you’ll need to operate your vehicle without this convenience feature. If you rely heavily on cruise control for long trips, plan accordingly. If the code is accompanied by other symptoms (such as additional warning lights or loss of other steering wheel controls), have it inspected promptly to rule out a larger electrical issue.

Vehicles most commonly affected by P0585 #

While P0585 can appear on almost any modern vehicle equipped with electronic cruise control, certain models appear more frequently in technical bulletins and service records. These vehicles often use multi-function switches or steering wheel controls that see a lot of use:

• Toyota Camry, Corolla, RAV4, and Tacoma
• Honda Accord, Civic, CR-V
• Ford F-Series, Focus, Fusion
• Hyundai Elantra, Sonata
• Lexus ES and RX
• Acura MDX, TL, RDX
• Chevrolet Silverado, Malibu
• Volkswagen Golf, Jetta

Note: This is not an exhaustive list; P0585 can occur on many other makes and models.

Common mistakes & best practices for P0585 #

One of the biggest pitfalls when addressing P0585 is replacing the cruise control switch without first confirming the root cause. Another is overlooking simple wiring or connector issues in favor of more expensive parts. Following a stepwise approach prevents wasted time and money.

• Don’t replace the switch until you’ve verified wiring and connector integrity.
• Always check for related codes that could indicate a shared wiring or clockspring problem.
• Use a wiring diagram and multimeter for accurate circuit testing.
• Inspect connectors for corrosion, especially if the vehicle is exposed to moisture.
• Clear the code and test drive after repairs to confirm resolution.

Express FAQ for P0585 #

Need a fast answer? Here are some of the most common questions drivers and techs ask about code P0585:

• Q: Will P0585 affect my ability to drive?
  A: No, your vehicle will operate normally, but cruise control will not function until the fault is repaired.
• Q: Can I fix P0585 myself?
  A: If you’re comfortable using basic tools and a multimeter, you can check for obvious switch, wiring, or connector issues. For more complex diagnostics or clockspring/ECU problems, professional help is recommended.
• Q: Is this code dangerous?
  A: Not directly, but the cruise control system won’t work, removing that convenience and possibly affecting long-distance driving comfort.